Stroke is the third largest cause of death in the United States. Over 700,000 strokes occur annually in the United States at an estimated cost of $40 billion annually. Of these, half are believed to be due to emboli originating at the carotid bifurcation. Large, multi-institutional trials confirm that surgery improves overall survival and stroke rates as compared to medical management for high-grade stenoses.
Duplex ultrasound (DUS) is one of the safest tests for the identification of significant degrees of carotid stenoses. While accurate, and safe, a high-quality DUS requires 20-40 minutes of technician time, formal physician interpretation, and costs several hundred dollars. Based on some studies, screening entire populations, even those limited to patients over 65, may be cost-ineffective unless the prevalence of carotid stenoses is at least 4.5%.
Many patients undergoing dental examination and/or treatment undergo panoramic radiography as part of their routine care. As is commonly known, a panoramic radiograph or an x-ray is an x-ray taken by a machine using a fixed and predetermined exposure setting that rotates around the head of a patient to give the dentists a picture of the patient's teeth, jaws and other important information. These radiographs (x-ray images) include, in most cases, the region of the carotid bifurcation on the sides of the resulting x-ray image. It has recently been noted that incidental calcifications can be visualized if adequate attention is paid to this area. Data suggest that the rate of clinically significant carotid disease may be high enough to make examination of this region on otherwise routine panoramic radiograph, followed by DUS, if positive, a clinically beneficial approach.
Initial research was carried out to understand the correlation between incidental findings on single view panoramic radiographs positive for carotid artery calcifications and clinically critical carotid stenoses. Data from the initial research suggest that the prevalence of clinically significant stenosis among patients for whom calcifications are observed on single view panoramic radiographs may be quite high; certainly well in excess of the 4.5% prevalence threshold at which the use of the DUS as a screening tool becomes cost effective.
The yielding of substantial public health benefits by being able to detect significant carotid stenoses using a single view panoramic radiograph depends in part on the improvement of the diagnostic quality of the panoramic radiograph or x-ray system. Intra and inter-examiner variability and misinterpretation of the carotid artery bifurcation have been proven to be dependent on the diagnostic quality of the x-ray image, suffering from the nature of the film/screen/imaging media configuration.
As panoramic radiographs were primarily designed to diagnose disease in the hard tissue regions within the maxillofacial region, soft tissue regions, such as those in the carotid artery region, tend to get overexposed or “burned,” when imaged using a single view panoramic radiograph. Radiographic filters exist to help improve contrast in radiographs of many types. While these filters tend to provide specificity and morphology, such filters tend to be site specific and unique in their filtering or contrast enhancing capabilities.
Therefore, in an effort to improve radiograph contrast and image quality in the carotid artery region, there is a need to develop a filter system for the carotid artery region.